Alien Arena 2008 is the ultimate freeware deathmatch game.
PrBoom+ is a Doom source port developed from the original PrBoom project.
A free, fast, browser based multiplayer shooter
It includes a lot of destructive enemies, an arsenal of weapons from simple pistols to missile launchers, traps, life-preserving armor and ambushes galore.
A tactical first person shooter with strong cartoonish atmosphere
A free first person shooter game written using JOGL
A 3D FPS written in JAVA + JOGL + JOGG
A project to create a complete Doom II-compatible IWAD file which is Free Software.